This invention relates to oil based well treating fluids and methods of using them; particularly for treatments involving transporting particles such as sand, gravel or fracture propping particles into openings in or around the borehole of a well. More particularly, the invention relates to a well treating fluid comprising a liquid mixture of aromatic and aliphatic hydrocarbons, polymers inclusive of at least one arene/diene block copolymer and at least one free radicalproducing polymer crosslinking agent.
In the text book "Block Copolymers" by D. C. Alport and W. H. James, John Wiley & Sons, 1973, on page 18 of the introduction, it is stated that, "Although a full understanding of the behavior of block polymers is not yet available, sufficient evidence has now been collected to draw conclusions which are general to all block copolymers in which dissimilar blocks are attached end to end. Several important classes of block copolymers now have significant commercial applications as elastomers, fibers, surfactants, adhesive and thermal plastics and the useful applications are steadily growing".
Numerous types of block copolymers have been described in the U.S. patents such as the following: U.S. Pat. No. 3,149,182, by L. M. Porter describes producing block copolymers by polymerizing a polyethylenically unsaturated hydrocarbon alkenyl-substituted aromatic hydrocarbons or alkenyl-substituted heterocyclic compound until there is no more unpolymerized monomer in the reaction mixture, then adding a dissimilar monomer of such a group and continuing the reaction. U.S. Pat. No. 3,333,024, by W. R. Haefele, C. A. Dallas and M. A. Diesz, describes similar block copolymers in which a portion of the unsaturation has been removed by hydrogenation to improve the thermal and oxidative stability of the polymers. U.S. Pat. No. 3,595,942 by M. W. Wald and M. G. Quam, describes selectively hydrogenated block copolymers which are solid at temperatures which liquefy block copolymers which are more or less hydrogenated. U.S. Pat. No. 3,682,187, by E. V. Seymour, S. Davidson and W. R. Haefell, describes block copolymers which are effective in reducing friction caused by flowing hydrocarbon liquids within conduits. U.S. Pat. No. 4,111,895, by W. P. Gergen and S. Davidson, describes the capability of block copolymers for stabilizing blends of dissimilar polymers. U.S. Pat. No. 4,116,917, by R. J. A. Eckert, describes the suitability of hydrogenated star block copolymers for altering the viscosity of liquid hydrocarbons. U.S. Pat. No. 4,120,915, by L. M. Fodor and A. G. Kitchen, describes styrene/conjugated-diene block copolymer compositions containing antioxidants for improving their thermal stability. The disclosures of these patents are incorporated herein by reference.
Oil based well treating fluids such as fracturing fluids are described in numerous United States patents such as the following: U.S. Pat. No. 2,794,779, filed about 30 years ago, (a) describes the need for a fracturing fluid to be thin enough to be readily pumped, yet thick enough to have a low fluid loss into the reservoir rock, and capable of spontaneously becoming thin enough for easy removal and (b) recommends use of aluminum salts of two ethylhexoic acids as thickening agents. U.S. Pat. No. 2,914,476 discloses tall oil soaps as thickening agents for oil based fracturing fluids. U.S. Pat. No. 2,946,748 discloses soaps of aliphatic acids containing more than 20 carbon atoms as thickening agents for oil based fracturing fluids. U.S. Pat. No. 2,966,457 discloses adding inorganic ammonium salts to oil based fluids along with alkali metal soap gelling agents. U.S. Pat. No. 2,988,505 recommends fracturing fluids comprising petroleum oils containing sparingly oil-soluble phosphates, sulphates, or sulfonates and asphaltenes as thickening agents. U.S. Pat. No. 2,997,441 suggests mixtures of calcium tallate soaps and calcium sulphates as thickening agents. U.S. Pat. No. 3,207,693 suggests calcium salts soap complexes mixed with small proportions of polyacrylic acids as thickening agents. U.S. Pat. No. 3,409,548 recommends cross-linked copolymers of alpha-olefins and sulfur dioxide as thickening agents. U.S. Pat. No. 3,466,242 recommends silica flour coated with ethylene-propylene copolymers as a thickening agent. U.S. Pat. Nos. 3,757,864; 3,990,978 and 4,200,539 relate to using aluminum soaps of partially esterified phosphoric acid as thickening agents. U.S. Pat. No. 4,200,540 suggests using aluminum salts of organic esters of phosphoric acid by dissolving one portion in the hydrocarbon liquid, as an initial thickening agent, and dispersing additional undissolved portions within the solution to provide a suspension having a viscosity which is initially relatively low but increases when the fluid is heated to a temperature at which a suspended aluminum salt dissolves, in order to extend the effective operating range to temperatures above about 200.degree. F.